Is it?

Bipedal is the easiest one: very few environments require 2 feet in particular. Sure, ability to cross uneven terrain is needed, but this can be done with 3, 4 or 8 feet. But in a lot of places, including most of the retail and a lot of factories, all one needs is an ability to move on flat surface and cross door thresholds (thanks to ADA, no stair climbing required). And than can work just fine with large wheels, or tracks. On the other hand with something like construction, you probably want many appendages with some sort of climbing attachments?

The "top" part of humanoid is more integrated into the world: our human infrastructure is really built for beings just under 2m high, and a many of actions need at least 2 human-like hands, with at least the same reach as humans (~3/8 body height long, attached at ~7/8 body height). But this is just a minimum - a lot of things would work better with 3 hands, or maybe with dissimilar hands - one "strong", one "fine manipulation" and one "misc"? I certainly wished to have a 3rd hand when building something...